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Events on Monday, November 23rd, 2020

Monday Science Seminar
Time: 12:00 pm - 1:00 pm
Place: Zoom:
Speaker: Goni Halevi (Princeton) and Theron Carmichael (Harvard CfA)
Abstract: Goni Halevi:
I’ll be talking about the interplay of MHD turbulence and nuclear burning in accretion disks formed by disrupted white dwarfs. This has relevance to binary systems that may contribute to optical transients and future gravitational waves sources.

Theron Carmichael:
Title: The search for transiting brown dwarfs with NASA's TESS mission
Traditionally, astronomers have separated giant planets from brown dwarfs based on the object's mass. Objects more massive than 13 Jupiter masses but less massive than 80 Jupiter masses are considered to be brown dwarfs. However, in detail, the lower mass threshold is 11 to 16 Jupiter masses depending on the metallicity of the object. This betrays how arbitrary a purely mass-based distinction between planets and brown dwarfs is. Instead, we take a critical look at the population of brown dwarfs for which we have the most fundamental information: transiting brown dwarfs. Transiting brown dwarfs provide us their mass, radius, and sometimes age, which makes them useful for directly testing substellar evolutionary models. Through a better understanding of how well these models describe the population of transiting brown dwarfs, we will develop a better definition of what makes a brown dwarf different from a giant planet: its formation mechanism. It is certainly true that in the mass range spanning between giant planets and low-mass stars that the dominant formation mechanism must change significantly. If we can determine which mass or distribution of masses that this change occurs at, then we will have a more physical way to distinguish planets from brown dwarfs. In this talk, we will review how the TESS mission has contributed to the transiting brown dwarf population so far, and we will examine a few specific examples of transiting brown dwarfs whose masses, radii, and ages have served as useful tests to substellar isochrones.
Host: Snezana Stanimirovic & Melinda Soares-Furtado
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Plasma Physics (Physics/ECE/NE 922) Seminar
Science Basis and Present Status of the new Divertor Tokamak Test facility
Time: 12:00 pm
Place: Zoom Meeting
Speaker: Piero Martin, University of Padova and Consorzio RFX, Padova, Italy; DTT Consortium, Frascati, Italy
Abstract: One of the high priority challenges for the exploitation of fusion as an energy source is the disposal of the non-neutronic energy and particle exhaust in a reactor. The new Divertor Tokamak Test (DTT) facility (its construction is starting in Italy) [1], is an experiment to address that challenge in high-field, high performance tokamak with full integration between core and edge plasma scenarios.

DTT is superconducting tokamak with 6 T on-axis maximum toroidal magnetic field carrying plasma current up to 5.5 MA in pulses with length up to 100s. The D-shaped device is up-down symmetric, with major radius R=2.19 m and minor radius a=0.70 m. The auxiliary heating power coupled to the plasma at maximum performance is 45 MW, shared between 170 GHz ECRH, 60-90 MHz ICRH and 500 kV negative ion beam injectors. This allows matching the PSEP/R values, where Psep is the power flowing through the last closed magnetic surface, with those of ITER and DEMO. DTT is in fact designed to reach PSEP/R =15 MW/m.

This talk will discuss the science basis for the experiment and the state of the art of the project. The presentation will start from the scientific background of the experiment, then will move to its main physics driver and finally will discuss the expected plasma scenarios - in particular as far as plasma exhaust is concerned. Emphasis will be given to highlight the effort of designing an experimental tool, which will be a device not only for plasma exhaust studies, but also for the advancement of fusion science in the grand sense.

[1] “DTT-Divertor Tokamak Test facility. Interim Design Report”, R. Martone, R. Albanese, F. Crisanti, P. Martin, A Pizzuto Eds. April 2019,

PAUL W TERRY is inviting you to a scheduled Zoom meeting.

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Host: Paul Terry
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